The present invention generally relates to devices and methods to treat an eye of a patient, and more specifically to intraocular implants that provide extended release of a therapeutic agent to an eye in which the implant is placed, and to methods of making and using such implants, for example, to enhance retinal function and/or to prevent retinal dysfunction.
Brimonidine, 5-bromo-6-(2-imidazolidinylideneamino) quinoxaline, is an alpha-2-selective adrenergic receptor agonist that is effective in the treatment of open-angle glaucoma by decreasing aqueous humor production and increasing uveoscleral outflow. Brimonidine is available in two chemical forms, brimonidine tartrate and brimonidine free base. Brimonidine tartrate (Alphagan P®) is available from Allergan, Inc., for treating glaucoma. Topical ocular brimonidine formulation, 0.15% Alphagan P® (Allergan, Irvine, Calif.), is currently commercially available for treatment of open-angle glaucoma. The solubility of brimonidine tartrate in water is 34 mg/mL, while the solubility of brimonidine freebase is negligible in water.
Recent studies have suggested that brimonidine can promote survival of injured retinal ganglion nerve cells by activation of the alpha-2-adrenoceptor in the retina and/or optic nerve. For example, brimonidine can protect injured neurons from further damage in several models of ischemia and glaucoma. See e.g. U.S. Pat. Nos. 5,856,329; 6,194,415; 6,248,741, and; 6,465,464.
Glaucoma-induced ganglion cell degeneration is one of the leading causes of blindness. This indicates that brimonidine can be utilized in a new therapeutic approach to glaucoma management in which neuroprotection and intraocular pressure reduction are valued outcomes of the therapeutic regimen. For brimonidine to protect the optic nerve, however, it must have access to the posterior segment of the eye at therapeutic levels. Currently available techniques for administering brimonidine to the posterior chamber of the eye are not sufficient to address this issue.
Biocompatible implants for placement in the eye have been disclosed in a number of patents, such as U.S. Pat. Nos. 4,521,210; 4,853,224; 4,997,652; 5,164,188; 5,443,505; 5,501,856; 5,766,242; 5,824,072; 5,869,079; 6,074,661; 6,331,313; 6,369,116; and 6,699,493.
It would be advantageous to provide eye implantable drug delivery systems, such as intraocular implants, and methods of using such systems, that are capable of releasing a therapeutic agent at a sustained or controlled rate for extended periods of time and in amounts with few or no negative side effects.